Bash: How to return from parent function if child function failed?

Question

I want to clean up some of my code, for that I want to clean the check return code status check I make after each command. If the command fails I return mid function to the parent function. If I'll take this code inside a function then nothing happens as the return command will be inside the new-child function.

Sure gald for some thoughts.

Current status:

a(){
    for i in $(cat file.txt)
    do
        scp $i hostb:/tmp/

        if [ $? -ne 0 ]
        then
            print_failed "SCP failed."
            return 1
        fi
    done
}

Desired:

a(){
    for i in $(cat file.txt)
    do
        scp $i hostb:/tmp/

        # continue as usuall unless return code is not 0
        check_status $?
    done
}

check_status(){
    if [ $1 -ne 0 ]
    then
        print_failed "SCP failed."
        return 1
    fi
}

Tom Fenech · Accepted Answer · 2018-04-10 08:26:20Z

2

As far as I'm aware, there is no implicit way to return from the parent function if the child function failed.

The closest thing I can think of would be something like this:

a () {
    while read -r source    # don't read lines with "for"!
    do
        check_status scp "$source" hostb:/tmp/ || return 1
    done < file.txt
}

check_status () {
    if ! "$@"
    then
        print_failed "SCP failed."
        return 1
    fi
}

The role of check_status is to execute a command and print the failure message if it didn't succeed. It also returns 1, so the parent function can use if ! or || to return as well.

There's no way of returning from the parent function except by using global variables, which I would personally avoid if possible.

To be honest though, I don't see the advantage of what you have over this:

a () {
    while read -r source
    do
        if ! scp "$source" hostb:/tmp/
        then
            print_failed "SCP failed."
            return 1
        fi
    done < file.txt
}

edited Apr 10, 2018 at 8:26

answered Apr 10, 2018 at 7:49

Tom Fenech

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5 Comments

Nir Over a year ago

The idea behinds it, it's all above code readness.. If there is still if in the parent function that check the return code, then it is not much different from the original code..

Tom Fenech Over a year ago

You could use exit instead of return but that would kill the whole script - is that what you want?

Nir Over a year ago

Can't use exit.

Tom Fenech Over a year ago

I edited to show a shorthand in the parent function but I think the simple answer to your original question is "no, it's not possible".

Nir Over a year ago

That's also an answer :)

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